A method and system for printer color calibration are disclosed, and more particularly, a combination of a full-width array (FWA) or similar page-scanning mechanism in conjunction with an spectrophotometer color measurement system in the output path of a color printing system for measuring colors wherein spatial color maps are used to adjust multi-dimensional color look-up tables to obtain good color correction of macro uniformity defects.
In many business applications, color documents have become essential as a component of communication. Color facilitates the sharing of knowledge and ideas. Companies involved in the development of color output devices continue to look for ways to improve the total image quality of such devices. One of the elements that affects the perception of image quality is an ability to consistently produce the same quality image output on a printer from one day to another, from one week to the next, month after month. Users are accustomed to printers and copiers that produce high quality color and gray scale output. Users further expect to be able to reproduce a color image with consistent quality on any compatible output device, including another device within an organization, a device at home or a device used anywhere else in the world. Hence, there remains a commercial need for efficiently maintaining print color predictability, particularly as electronic marketing has placed more importance on the accurate representation of merchandise in illustrative print or display media.
Color rendering devices (e.g., a printer, copier, or other image output device) often have problems with macro uniformity defects, like streaks, banding, “smile/frown” defects, etc. Recently filed patent application, U.S. application Ser. No. 11/170,928, filed Jun. 30, 2005, entitled “SYSTEM AND METHOD FOR SPATIAL GRAY BALANCE CALIBRATION USING HYBRID SENSING SYSTEMS,” by R. Enrique Viturro, et al. (which application is hereby incorporated by reference for its entire teachings) shows how to develop a spatial map of gray balanced TRC's (Tone Reproduction Curves) built by in-line spectral photometers. Hybrid sensing is employed to obtain mapping of the spatial gray balance TRCs to correct for the macro uniformity defects. In the development disclosed therein, implementation of spatial maps is accomplished with a sensing system composed of a spectral photometer (LCLED) producing a point wise gray balance TRC, and a full-width array RGB scanner giving information required for obtaining delta (errors) maps required to proliferate the gray balance TRC to every pixel. However, there is no suggestion in the application of extending such a spatial gray balanced calibration to a system of spatial color control methodology. Gray balance provides one-dimensional correction (e.g., corrections to neutral or gray axis) with other color axes not fully corrected. Accordingly, there is a need for calibrating printers with a spatial color control methodology for mapping LUTs to a spatial domain based on the developability state of colors on an output printed sheet.
More particularly, there is a need for a sensing system comprising a spectrophotometer (e.g., low cost light emitting diode (LCLED) spectrophotometer) and the use of uniformity measurements for a full-width array (FWA) scanner bar to measure developability nonuniformity on a photoreceptor or transfer belt. Such devices in combination are suitable to provide a printer or similar output device with macro defect detection and correction capabilities. Control algorithms achieving a spatial mapping for adjusting multi-dimensional LUTs effectively calibrate an output device spatially whereby the device can produce a more uniform color for a calibrated output image.